Electronic printers, such as thermal printers, laser printers, and ink-jet printers, are used to print on a wide range of print media in a variety of applications. For example, printers are typically used as output devices for personal computers. Another important application of printers is in the printing of symbologies such as bar codes.
Depending upon the specific application, a variety of print media may be used in bar code printers. For labeling of products in inventory applications, for example, bar codes are often printed onto label stock of varying thicknesses and surface textures. The particular type of print medium can significantly affect the quality of print achievable by a printer and can also affect the selection of operating parameters of the printer.
In certain applications, the selection of printer operating parameters may also be affected by the type of image being printed. For example, there are a range of quality levels that can be selected for a bar code image. The American National Standards Institute (ANSI) defines the quality of bar code image in ANSI standard Guidelines For Bar Code Print Quality, developed by committee X3A1.3 and MH10.8. The ANSI quality grades are letter grades that include A, B, C, D, and F where A is the highest grade and F is a failing grade. A bar code image having a quality grade of A must have certain defined characteristics, while a lower quality bar code image having a quality grade of C must meet less stringent standards. The quality of the bar code image can be controlled by the proper selection of the print medium and the proper selection of printer operating parameters to be used when printing on that print medium, such as print speed, print head pressure, and burn time. Burn time is the length of time that a printing element in a thermal print head is energized to cause a portion of the output image to appear on the print media.
In most prior art printers, the printer operating parameters are selected and manually entered by the user .for the particular printer and the particular print medium selected for use, often on a trial and error basis. The user typically chooses the printer operating parameters by entering information using buttons on the printer. This process is slow and tedious. Such printers generally have limited user interface capability, and printer operating parameter selection is accomplished by selecting menus and selecting parameters within these menus. The user must have an extensive experience in the operation of the particular printer, as well as experience in selecting the printer operating parameters for the selected print medium.
Many times printers are coupled to a host computer using a computer interface, such as an RS-232 interface. The host computer downloads the printer operating parameters rather than the user manually entering the parameters through a menu on the printer itself. This is sometimes accomplished with a label design software package. While the user interface in such printing system may be more sophisticated, the user must still have experience in the use of the printer and host computer, as well as experience in selecting the appropriate printer operating parameters for the selected print medium.
After a period of trial and error in selecting the appropriate printer operating parameters, the printer should print bar codes with an acceptable quality level. However, changes in operating conditions, such as a change in the ambient temperature or a change in temperature at the print head, may change the quality of the output image and result in an unacceptable image. A bar code verifier, well known in the art, can be used to scan and analyze the output image to provide an ANSI grade for the particular image. To compensate for changes in the quality of the output image, the user must manually alter the printer operating parameters or alter them using the RS-232 interface described above. The alteration of printer operating parameters to compensate for changes in operating conditions also requires a great deal of experience to correctly determine which operating parameters should be adjusted and how much they should be adjusted.
When another type of print medium is selected for the next print job, the entire process must be repeated for the new print medium. Prior art printers do not provide a simple technique for changing printer operating parameters to accommodate changes in print media or for altering the printer operating parameters to compensate for changes in operating conditions. For good quality results in reasonable time the user must have extensive knowledge of the particular printer being used, the type of print media to be used with the particular printer, and a knowledge of the operating system if a host computer is used to control the selection of printer operating parameters.
A typical prior art printing system is illustrated in FIG. 1. A host computer 2 controls the operation of both a bar code printer 4 and a bar code reader 6. The printer 4 and the reader 6 are separate devices that are independently coupled to the host computer 2. The printer 4 is coupled to the host computer 2 through a printer interface 8. A printer power supply 10 provides the necessary electrical power to the printer interface 8 and a print engine 12. The print engine 12 is the portion of the printer 4 that actually produces the output image on the print medium. Many different types of print engines 12 can be used with the printer 4.
The reader 6 is coupled to the host computer 2 through a reader interface 14. A reader power supply 16 provides the necessary electrical power to the reader interface 14 and a scan engine 18. The scan engine 18 can be used to scan the output image of the print medium and read or decode the information encoded in the output image. The host computer 2 controls the operation of the printer 4 and the reader 6. There is no direct communication between the printer 4 and the reader 6. In other prior art systems, the printer 4 and the reader 6 are standalone devices that do not utilize or require the host computer 2. The standalone printer and the standalone reader do not communicate with each other and have no interactive capabilities. To verify the quality of an output image, with a prior art system, the user must manually take the print medium with the output image to the verifier to verify the quality of the output image. The verifier may be a standalone device or may be integrated with the host computer 2 using the reader 6 to scan the output image. However, the user must still adjust the printer operating parameters in the manner described above if the output image cannot be read or does not meet the desired level of quality.
The extensive knowledge of the printer and print media required of a user by the prior art, together with the tedious process of manually selecting or adjusting printer operating parameters, make it difficult to switch from one type of print medium to another, or to adjust the operating parameters to compensate for changes in printer operating conditions. Therefore, it can be appreciated that there is a significant need for a printing system that simplifies the selection of printer operating parameters and maintains the desired quality level of the output image.